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GordonW
03-25-2004, 08:57 PM
One small step for hi-fi repair, one giant leap for listening fun!!

About 6 months ago, I was given an Harman-Kardon Award A300 tube integrated amp. When I got it, it ALMOST worked... one channel would actually play clearly, with the better 2 of the 4 output tubes in it, but the other channel wouldn't play properly at all... determined it was a bad volume control, some bad coupling caps, and at least one bad output tube.

Well, this would be a relatively routine job, but:

1- the volume control pot was ONE MEGAOHM. One megaohm? 100K, fine, no problem finding those. Even 250K! But try finding ANY dual-gang audio taper 1 megahom pot these days?!

2- 7408? WTF? I had never heard of that. Finally found some people (thanks TA and TE!!) who could DEFINITIVELY tell me that it was EXACTLY the same as a 6V6GT... like, NO PROBLEM finding those, once I actually knew what they were supposed to be. Too bad I spent the better part of a month, under the false impression that the amp was supposed to have 7355 outputs, and searching for THOSE (and actually FINDING some, anyone need some 7355s? :banghead: )

Well, I finally found a pot (from Mouser, it ain't a great one in comparison to Bournes, ALPS and the like, but hey, IT WORKS!), and got hold of some NOS JAN 6V6GT tubes... put the pot and the tubes in today...

HOLY COW this amp sounds GREAT!

I was expecting a GOOD amp, but I swear- this may be one of the top 5 best sounding phono stages in this amp, I've EVER heard, at ANY price. We're talking Audio Research levels of sonic refinement, IMHO.

Also, the USEFULLNESS of the tone controls is striking. Most tone controls are WORSE than useless, usually... but these do a nice "tilt up" or "tilt down" on the ends of the spectrum. Works wonders on taking care of speaker/room combos that sound "thin" or "tubby"!

Overall, just the plain TRANSPARENCY of the amp, is really something else. Sometimes, just having EVERYTHING all in one box, is the WAY TO GO... a simple circuit, executed MASTERFULLY. There are LOTS of amp/preamp combos for many multiples of the retail price of this amp, these days, that just "get in the way" of the sound, in a way that this amp DOESN'T. Dynamic, open, images like a MF, neutral, solid, stable... heck, other than it not being 200w/ch, what more could anyone ask for??

This little trooper has found a permanent home. Somebody would have to offer me a BUNCH of money, to get this one out of my hands now!

Regards,
Gordon

Hofmannhp
03-28-2004, 02:14 AM
Originally posted by GordonW
............. One megaohm? 100K, fine, no problem finding those. Even 250K! .............
Regards,
Gordon

Hi Gordon,

since several months I try to find 250K, log Pots tandem, with toothed axis.....do you have an idea where I can get them.

HP

GordonW
03-28-2004, 07:40 AM
They're cheap... not what I'd call "high end"... but Mouser Electronics is where I got my pot from, and they also had 250K dual-gang log-taper (audio taper) pots.

None of them had a splined/knurled (toothed?) shaft tho... fortunately, I had enough room (between the back of the faceplate and the panel behind that, where the pot mounted) to do a "splice"... by cutting off the splined shaft of the original dead pot with a Moto-Tool and a cutting wheel, shortening up the smooth shaft of the new pot the same way, using a piece of 1/4" tubing as a "splint" over the joint between the two parts, and filling up the inside of the tubing with glue (I used accelerated super glue, epoxy would also work well), to bond the original shaft onto the new pot, so I could put the original knob back on.

I think you should have an easier time finding 250K pots, than I had finding a 1meg pot, tho... I'd try Michael Percy Audio (they do have a web site, unfortunately I don't have the address handy... but you should be able to just put "Michael Percy Audio" into the search window of Google and find it). Bet they have one you can use.

Regards,
Gordon.

Hofmannhp
03-29-2004, 01:51 AM
Originally posted by GordonW
... but Mouser Electronics is where I got my pot from, and they also had 250K dual-gang log-taper (audio taper) pots.

......splined/knurled (toothed?) shaft tho... fortunately,............just put "Michael Percy Audio" into the search window of Google .....
Regards,
Gordon.

thanks Gordon, I try it there...."percyaudio.com"

HP

Chas
04-25-2004, 04:19 PM
Overall, just the plain TRANSPARENCY of the amp, is really something else. Sometimes, just having EVERYTHING all in one box, is the WAY TO GO... a simple circuit, executed MASTERFULLY

I had an A50K, the one WITH the 7355's :D These things had nice output iron even though there were no UL taps. In around 1985 I ended up building a nice EL34 triode class A (yeah, I know-overkill) stereo headphone amp for use with my Stax SRX Mk III/SRD-7. A few years ago I replaced this with an Stax SR-Lambda signature set up with a tube based energizer.

The old amp and headphones are still in use today sounding great in a friend's system.